Along with the continuous growth of the Internet, various network services come forth one after another, and various advanced multimedia systems emerge endlessly, which makes the Internet frequently process various multimedia services, such as File Transfer Protocol (FTP) service that is highly sporadic, and Hypertext Transfer Protocol (HTTP) service containing image files. As real-time services in networks are sensitive to network characteristics including transfer delay and delay jitter, the quality of the real-time services will be affected while the network is processing such multimedia services as FTP and HTTP services. Moreover, multimedia services always occupy much bandwidth, so that enough bandwidth couldn't be provided continuously for transferring key services reliably.
To solve the above problems, various Quality of Service (QoS) technologies have been brought forth. For instance, Internet Engineering Task Force (IETF) has established many service models and mechanisms to meet the demands of networks. Among the QoS technologies, the most recognized technical solution is to adopt the Integrated Services (Int-Serv) model at the access and edge of the network and adopt the Differentiated Services (Diff-Serv) model at the core of the network. As QoS is guaranteed only by setting priority levels in the Diff-Serv model adopted to the solution, it is hard to guarantee the transfer reliability and transfer quality in the network in spite of the high efficiency of utilizing the lines.
To solve the problem, an independent bearer control layer is introduced into the prior Diff-Serv model. An improved Diff-Serv model is brought forward to take the place of the prior Diff-Serv model, with an independent bearer control layer and a set of corresponding Diff-Serv QoS signaling mechanism. For example, to promote the application of the Diff-Serv, a Bandwidth Broker (BB) model is used to realize management of network resources and topology in the QBone Experimental Network jointly promoted by IETF, manufacturers and research institutes. Besides, some other manufacturers have brought forward some similar techniques of QoS server/resource manager to manage the topology and resources and coordinate QoS capabilities in different Diff-Serv domains.
A Diff-Serv model with the independent bearer control layer is illustrated in FIG. 1. The bearer control layer in this model consists of several bearer network resource managers (CMs), which can be Bandwidth Brokers, QoS servers, or other network devices. While processing a service bandwidth request from a user, the bearer control layer needs to designate the path of the user service, then a CM will instruct an edge router (E) to establish a Label Switching Path (LSP) according to the designated path and the service flow is forwarded through this LSP.
The route forwarding solution in the prior art for the bearer network to forward service flow through the path specified by the bearer control layer mainly includes: establishing a LSP by means of resource reservation according to the Multiple Protocol Label Switching (MPLS) technology along the path of service flow specified by the bearer control layer, then conducting route forwarding through the LSP. In other words, the bearer network needs to reserve bandwidth according to the explicit route mechanism of MPLS to establish an end-to-end LSP, and then conduct route forwarding through the LSP. The signaling protocol provided by the explicit route mechanism of MPLS can be RSVP-TE or CR-LDP.
A typical route forwarding solution is hereinafter described in detail. The established LSP in accordance with the solution is illustrated in FIG. 2. The detailed description of the steps of this solution is as follows:
Step A: the bearer control layer assigns a bearer path according to the service bandwidth request from a user, which is to specify the path information including the intermediate routers and interfaces in the bearer network through which the service flow is transferred; and then send the specified path through control signaling to the starting router in the bearer network.
For example, as illustrated in FIG. 2, the bearer control layer assigns the path E1→A→B→C→D→E2 to the service flow from the router E1 to the router E2, and sends this path information to the starting router E1.
Step B: the starting router E1 in the bearer network makes bandwidth reservation for the current service request of the user according to the explicit route signaling of MPLS, and establishes an end-to-end LSP.
Along with the path assigned by the bearer control layer through the routers E1, A, B, C, D and E2, an end-to-end LSP, i.e. the LSP from the router E1 to E2, has to be established among these routers in order to transfer the service flow from the router E1 to E2. The detailed description of the establishing process for the LSP is given as below. The starting router E1 determines the path from the router E1 to A for the LSP, and sends the path information containing a request for binding labels to the specific LSP to the transfer router A through the explicit route signaling of MPLS. The handling process of the sequent transfer routers, including A, B, C and D, is similar to the above process for establishing the LSP from the router E1 to E2. A label is distributed to the corresponding upstream router by each downstream router in the link when the link is established to form the end-to-end LSP. After the label switching path has been established between the routers D and E2 by means of a label being distributed to the router D by the router E2, the router D returns the information of the path established by itself to the router C, then the router C returns the information of the path established by itself and the router D to the router B, and such a process is repeated accordingly, and all the path information contains label information. Therefore, the starting router E1 finally obtains the complete LSP information including the label information of the end-to-end LSP.
Step C: when the service flow enters the starting router E1, the router E1 attaches the designated LSP label to this service flow. The service flow is forwarded through the end-to-end LSP established in Step B.
To be specific, every router through which this end-to-end LSP passes maintains the corresponding label information of the LSP, therefore every router may forward the service flow directly according to the label.
It can be seen from the above solution that the LSP is created or updated in the conventional bearer network for the service bandwidth request of a user by means of the explicit route signaling technique of MPLS according to the path assigned by the bearer control layer, and the service flow is forwarded in the bearer network through the LSP, therefore the service flow in the bearer network can be forwarded through the path assigned by the bearer control layer.